STAURASTRUM. 57 



arranged in horizontal and vertical series across the faces 

 of the semicell. Vertical view triangular, sides straight 

 or slightly convex, each with about 8 spines along the 

 margin ; apex of semicell provided with 2 or 3 series of 

 spines parallel to the marginal one, centre of apex smooth. 



Zygospore unknown.* 



Length 33 p. : breadth 28 ^ ; breadth of isthmus 

 12'o (JL ; length of spines about 2'5 JJL. 



WALES. Capel Curig, Carnarvonshire (Roy}. 



SCOTLAND.- -Verv rare ; near New Pitslio-o. and South 



/ 



of Birsemore. Aberdeen ; Canlochan, Forfar ; Bracklin, 

 Perth (Roy & Bus.). 



Geogr. Distribution. France. Germany. Switzerland. 

 Galicia in Austria. Servia. Xorway. Sweden (form). 

 Poland. Central Russia. Faeroes. Greenland. ? India. 

 ? Siam. E. and Central Africa. United States. Alaska. 



Fig. 12, PL CXXXVIi; is copied from a drawing by the late 

 Dr. Lutkemiiller made by him from de Brebisson's original 

 exsiccata. It certainly agrees more with de Brebisson's figure in 

 Kalfs' ' British Desmidiese ' than any other figure previously 

 published. St. eclrinatum had never been observed in Britain by 

 either the late Professor G. S. West or W. West, and the figures 

 published by them of specimens from Koh Chang and Africa 

 obviously deviate considerably from the type, and were only 

 referred to this species after much deliberation. They would 

 possibly be more correctly placed in some other species. A very 

 characteristic feature of St. echitmtiun is the peculiar and sudden 

 dilatation of the spines at their base (see in this connection the 

 figure of Borge in ' Botan. Xotiser,' 1913, t. 3, f. 36, which also 

 gives some indication of this character). 



83. Staurastrum gladiosum Turn. 

 (PL CXXXVII, figs. 1, 2.) 



St. gladiosum Turn. Xew Rare Desm. 1885, p. 6, t. 16, f. 21 ; De Toni, 

 Syll. Alg. 1889, p. 1172; West, Alg. X. Wales, 1890, p. 16, West & G. S. 

 West, Alg. 8. England, 1897, p. 494. 



* Gronblad (' Desm. Keuru,' 1920, p. 62, t. 1, f. 38-40) figures a Staurastrum 

 with zygospore which he refers with some doubt to St. echinafnm Breb. In 

 the opinion of the writer this Desmid does not belong here, since the spines 

 are far too long. The zygospore has therefore been ignored. 



